Some biochemical and histochemical properties of human liver serine dehydratase
Some biochemical and histochemical properties of human liver serine dehydratase
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DOI：
10.1016/j.biocel.2004.08.004
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发表时间：
2005-03-01
影响因子：
4
通讯作者：
Pitot, HC
中科院分区：
文献类型：
--
作者：
Kashii, T;Gomi, T;Pitot, HC
在大鼠体内，丝氨酸脱水酶(SDH)在肝脏中含量丰富，是一种糖异生酶，而人肝脏丝氨酸脱水酶含量低，难以获得新鲜材料，对其生化性质的研究较少。为了解决这些问题，我们从大肠杆菌中纯化了重组酶，并比较了人和大鼠肝脏丝氨酸脱水酶的一些性质。Edman降解表明，约75%的人丝氨酸脱水酶的N-末端序列开始于Met(Start)-Met(2)-Ser(3)-，其余的开始于Ser(3)-，而大鼠酶的N-末端始于Met(STA RT)-Ala(2)-的第二密码子。纯化后的制剂经质谱分析完全证实了其异质性。因此，这一观察在一定程度上没有遵循当倒数第二个氨基酸的侧链较大时第一个Met不被去除的一般规律，如Met、Arg、Lys等。用胰酶和金黄色葡萄球菌V8酶进行有限蛋白分解实验表明，两种酶的局部结构存在明显的差异。最显著的区别是组织化学：大鼠肝脏丝氨酸脱水酶仅在门静脉周围区域表达，许多参与糖异生和尿素循环的酶在该区域共存，而人肝脏丝氨酸脱水酶主要位于静脉周围区域。这些发现为生理学实验提出的先前的观点提供了额外的支持，即在人类肝脏中，丝氨酸脱水酶对糖异生的贡献可以忽略不计或很小。(C)2004爱思唯尔有限公司。保留所有权利。
In rat, serine dehydratase (SDH) is abundant in the liver and known to be a gluconeogenic enzyme, while there is little information about the biochemical property of human liver serine dehydratase because of its low content and difficulty in obtaining fresh materials. To circumvent these problems, we purified recombinant enzyme from Escherichia coli, and compared some properties between human and rat liver serine dehydratases. Edman degradation showed that the N-terminal sequence of about 75% of human serine dehydratase starts from Met(START) -Met(2) -Ser(3)- and the rest from Ser(3)-, whereas the N-terminus of rat enzyme begins from the second codon of Met(STA RT) -Ala(2)-. The heterogeneity of the purified preparation was totally confirmed by mass spectrometry. Accordingly, this observation in part fails to follow the general rule that the first Met is not removed when the side chain of the penultimate amino acid is bulky such as Met, Arg, Lys, etc. There existed the obvious differences in the local structures between the two enzymes as revealed by limited-proteolysis experiments using trypsin and Staphylococcus aureus V8 protease. The most prominent difference was found histochemically: expression of rat liver serine dehydratase is confined to the periportal region in which many enzymes involved in gluconeogenesis and urea cycle are known to coexist, whereas human liver serine dehydratase resides predominantly in the perivenous region. These findings provide an additional support to the previous notion suggested by physiological experiments that contribution of serine dehydratase to gluconeogenesis is negligible or little in human liver. (C) 2004 Elsevier Ltd. All rights reserved.